<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>变量</title>
</head>
<body>
    <script>
        // 声明变量
        let age;
        // age变量赋值为18
        age = 18;
        // age = '你好'；
        // 输出age变量
        alert(age);
        console.log(age);
        
    </script>
</body>
</html>